The biomedical research community regards The Jackson Laboratory (TJL) as a leading resource for unique genetically defined mice for use in highly specialized research applications. The collection of over 2700 strains includes nearly 800 strains that are distributed in low but steady numbers. The demand is constant enough that live breeding colonies, rather than cryopreserved germplasm, is the most economical means of maintenance. These strains are distributed to nearly 1000 investigators at 700 institutions. The colonies that comprise TJL's repository of low-demand strains are now housed in 16 different mouse rooms, some of which do not have the capability for sterile supply delivery. The physically dispersed resources make it difficult to implement consistent management paradigms that will ensure mice are delivered to investigators who request them at reasonable cost and within a reasonable period of time. A year-long planning group has recommended that the collections of strains be consolidated into a single, dedicated Jackson Laboratory Repository in which optimal management practices can be employed and Repository mice can be maintained in a high-level barrier facility supplied with sterile materials. Funds are requested to renovate two existing animal rooms of 2191 ft(2) each to upgrade the barrier status and to purchase an air shower for each room, 20 HEPA-filtered, ventilated changing stations, and two laminar flow hoods.